METHOD FOR SEALING AN ANNULAR SPACE IN A WELLBORE

Description

FIELD OF THE INVENTION

[0001] The present invention relates to the field of oil recovery from a wellbore.

BACKGROUND OF THE INVENTION

[0002] For oil recovery a well is drilled and a well tubular such as a casing or a liner is introduced into the well. The outside diameter of the well tubular is smaller than the inside diameter of the wellbore, thereby forming an annular space between the well tubular and the wellbore. The well tubular is perforated at one or more zones in order to facilitate the flow of hydrocarbons into the tubular and subsequent flow upstream for recovery. Occasionally contaminating materials such as water and sand are produced along with the hydrocarbons from a part of the subterranean formations surrounding the well tubular. In these situations it is desirable to seal off the well tubular from one or more parts of the annular space. Also, in other situation it may be desirable to seal off the annular space.

[0003] To seal off a desired part of, e.g., a well one possibility is to isolate the internal part of the well tubular using temporary packers. Cement or another hardenable composition is then pumped down to the isolated zone to seal the perforated openings in the desired part of the well tubular. If production is subsequently desired from a zone situated further downstream in the casing, removal or penetration of the seal is required.

[0004] In the past, the placing of a "treatment fluid", e.g., an acid, a polymer, or cement, within a wellbore, has been accomplished by use of a "bailer", which is introduced into the well on a wireline or the like. The bailer contains a specific volume and is activatable due to density differential of the treatment fluid relative to the natural fluids present in the wellbore at the time and location of treatment. Even modified bailer systems do not satisfactorily deliver a predetermined amount of a treatment fluid at the exact location, especially in highly deviated wells or in the well tubular which has become "cork-screwed". Thus, a number of other systems have been devised for deploying a "treatment fluid" at a proper location for e.g. providing a seal.

[0005] US 6,955,216 discloses a device for injecting a fluid into an earth formation surrounding a well. The device comprises a body suitable for being arranged in a well bore and provided with a fluid chamber for storage of suitable sealant and a pair of inflatable packers arranged to isolate a portion of the well bore between the packers upon inflating the packers. The suitable sealant is then injected under pressure into the formation through perforations isolated between the packers. The sealant composition is disclosed to be a suitable material, such as a vulcanised or unvulcanised rubber composition.

[0006] US 4,972,906 discloses the use of a mixture of a liquid epoxy material and a hardener for plugging a zone in a subterranean zone. The epoxy material used is heavier than the fluid in the well, and it is further characterized as being free of solids and having a low viscosity at downhole temperature and pressure. The material is placed in a well by the use of a positive displacement bailer. Hence, the liquid epoxy material exhibit an undesirable axial dispersion, which may only partially be overcome by using an excessive amount of the epoxy material. Thus, the method has the drawback of not facilitating a site-specific placing of the seal.

[0007] US 2006/0234871 discloses a method of plugging a permeable zone in a wellbore using a sealant composition comprising one or more gel systems, a leak prevention material, water, and optionally a fluid loss control additive.

[0008] US 2007/0227733 A1 discloses a method of forming a seal circumferentially about a liner having pre-formed openings that is positioned in a wellbore including the steps of running a perforating device and a seal applicator into the slotted liner, the seal applicator carrying a sealing fluid and a pumping mechanism, creating an aperture through the slotted liner at the region by activating the perforating device and pumping the sealing fluid from the seal applicator through the aperture and circumferentially about the liner to form a sealing plug in the annulus between the slotted liner and the wellbore.

[0009] WO 2005/078234 A1 discloses a method for suppressing fluid communication to or from a wellbore in a subsurface formation, which method comprises providing a well fluid which comprises solid particles in a carrying fluid, which solid particles include a reactive polymer; introducing the well fluid into the wellbore so that carrier fluid passes through an interface between the wellbore and its surroundings, wherein particles are accumulated at the interface; and allowing the polymer to form a solid plug suppressing flu 5 id communication through the interface; and a well fluid for use in a wellbore, which well fluid comprises solid particles in a carrying fluid, which solid particles include a reactive polymer.

[0010] EP 0 898 050 discloses a method of sealing a pipe in a wellbore, wherein the method comprises placing a hardenable epoxy sealing composition, which hardens into a resilient solid mass and comprises an epoxide-containing liquid, an organosilane compound and a hardening agent, into the annulus between the pipe and the walls of the wellbore.

[0011] Thus, there is a need to devise improved procedures for introducing a seal in an annular space between a well tubular and the surrounding formation.

SUMMARY OF THE INVENTION

[0012] In order to overcome the above-mentioned limitations of the known methods for providing a sealing, the present invention provides a method for providing one or more seals in an annular space between a well tubular and the surrounding formation or between pipes of a wellbore system, said method comprising the steps of

a) determining the in-situ temperature, pressure, earth formation properties, and fluid(s) present at the position(s) where said one or more seals are desired,

b) providing a sealing substance which is a setting epoxy based, phenolic based, or polyester based fluid comprising at least one solid component and said sealing substance having physical and fluid dynamic properties compatible with the in-situ parameters determined in step a), wherein the density of said sealing substance is in the range from 700 kg/m³ to 1400 kg/m³, and said sealing substance has a density, which is either lower or higher than the density of the fluid(s) determined in step a),

c) placing said sealing substance at one or more locations allowing it to flow into the annular space and undergo curing to form said one or more seals,

wherein the sealing substance has thixotropic properties, which are compatible with the parameters determined in step a).

[0013] According to the invention, the sealing substance has thixotropic properties, which are compatible with the parameters determined in step a). By using a sealing substance, which is thixotropic, it has been found that the coherence of such a sealing substance provides for unique properties in relation to dispersion of the fluid, in particular to enable the fluid to flow around the whole diameter of a tubular without slumping or excessive dispersion outwards from said tubular.

[0014] The present invention now provides a process for providing one or more seals with great precision and without introducing excessive amounts of sealing substance into said annular space.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] 

Figure 1 shows the injection system comprising two deformable cartridges each containing a fluid. In the case of a two component system this will be a base fluid and a hardener. The fluids are being extracted from the cartridges using positive displacement pumps. These pumps are driven by a single motor and each pump has a pre-determined displacement per revolution thus enabling the definition of the mixing relation between the fluids. A similar design can be made for fluid systems consisting of a single or more than two components.

1: housing with holes allowing wellbore pressure to enter the housing

2: deformable tube filled with the substance

3: internal rod with holes allowing the substance to access the pump (4)

4: pump with internal valve

5: electric motor driving both pumps (4 and 7)

6: exit line of the pump (4)

7: pump with internal valve

8: deformable tube filled with the substance

9: housing with holes allowing wellbore pressure to enter the housing

10: exit line of the pump (7)

Figure 2 shows the displacement sequence of the fluids when displaced into the annular space formed by the wellbore (2) and well tubular (1). The areas (3), (4), (5), (6), and (7) represent the progression of the fluid during the displacement in steps randomly taken from the video tapes. Figure 2 shows that the fluid stays together, i.e. is not slumping nor mixing during the displacement. The time it took to displace 15 liters into an annular space of 3.81 cm (1.5 inch) is some 10-20 minutes. This time can be varied by using different motor and pump combinations. During the time that the fluid is being displaced into the annular space 'hardening' of the fluid will be prevented by using retarding chemicals.

1: inner tube, representing the liner in the well bore

2: outer tube, representing the well bore wall

3: stage 1 of filling

4: stage 2 of filling

5: stage 3 of filling

6: stage 4 of filling

7: final fill

8: fill nozzle

9: fill tube

DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention provides a method for providing one or more seals in an annular space between a well tubular and the surrounding formation or between pipes of a wellbore system, said method comprising the steps of

a) determining the in-situ temperature, pressure, earth formation properties, and fluid(s) present at the position(s) where said one or more seals are desired,

b) providing a sealing substance which is a setting epoxy based, phenolic based, or polyester based fluid comprising at least one solid component and said sealing substance having physical and fluid dynamic properties compatible with the in-situ parameters determined in step a), wherein the density of said sealing substance is in the range from 700 kg/m³ to 1400 kg/m³, and said sealing substance has a density, which is either lower or higher than the density of the fluid(s) determined in step a)

c) placing said sealing substance at one or more locations allowing it to flow into the annular space and undergo curing to form said one or more seals,

wherein the sealing substance has thixotropic properties, which are compatible with the parameters determined in step a).

[0017] The sealing substance is an epoxy, phenolic or polyester based fluid. Such setting liquids are well known in a wide number of industrial applications and they are commercially available as a vast number of different compositions. For instance, an epoxide containing liquid may be selected from the group of the diglycidyl ether of 1,4-butanediol, the diglycidyl ether of neopentyl glycol, the diglycidyl ether of cyclohexane dimethanol and mixtures thereof. In one embodiment the epoxy is comprised of epichlorohydrin and bisphenol A. It will be appreciated that a mixture of different epoxides may also be used for the sealing substance. Likewise, it will be appreciated by those skilled in the art that a number of phenolic and polyester based fluids may also be used. The sealing substance may comprise an epoxy, phenolic, or polyester contents in the range from about 10% to about 95% by weight, or from about 20% to about 80% by weight, or from about 10% to about 75% by weight, or from about 10% to about 50% by weight, or from about 30% to about 80% by weight, or from about 40% to about 80% by weight, or from about 60% to about 75% by weight.

[0018] Suitable hardening agent for epoxy is at least one member selected from the group of aliphatic amines, aromatic amines, and carboxylic acid anhydrides. Non-limiting examples of such hardening agents for epoxy based fluids are aliphatic amines, aromatic amines, amide amines, amido amines, imidazoles, and carboxylic acid anhydrides. Examples of hardening agents for epoxy fluids are triethylenetetraamine, ethylenediamine, N-cocoalkyltrimethylenediamine, isophoronediamine, diethyltoluenediamine, and tris(dimethylaminomethylphenol). These hardening agents may be present in said epoxy fluid in an amount in the range of from about 15% to about 40% by weight of said fluid.

[0019] In one embodiment the sealing substance has thixotropic properties, which are compatible with the parameters determined in step a). By using a sealing substance, which has thixotropic properties, it has been found that the coherence of such a sealing substance provides for unique properties in relation to dispersion of the fluid, in particular to enable the fluid to flow around the whole diameter of a tubular without slumping or excessive dispersion outwards from said tubular.

[0020] The thixotropic properties of an epoxy, phenolic, or polyester based fluid may be controlled by various additive, e.g. by addition of silica flakes to increase the thixotropic properties or by addition of acetone to decrease the thixotropic properties. In another embodiment the sealing substance comprises silica flakes. In another embodiment the sealing substance comprises carbon fibres. In another embodiment the density of said sealing substance is in the range from 700 kg/m³ to 1400 kg/m³, such as in the range from about 800 kg/m³ to about 1200 kg/m³, in the range from about 900 kg/m³ to about 1100 kg/m³, in the range from 700 kg/m³ to about 900 kg/m³, in the range from about 900 kg/m³ to about 1200 kg/m³, or in the range from about 1000 kg/m³ to about 1200 kg/m³.

[0021] In yet another embodiment the sealing substance has a density which is lower than the density of the fluid(s) determined in step a). In this case the sealing substance may be introduced into the one or more locations at a lower vertical position than the annular space into which said sealing substance is to flow.

[0022] In yet another embodiment the sealing substance has a density which is higher than the density of the fluid(s) determined in step a). In this case the sealing substance may be introduced into the one or more locations at a higher vertical position than the annular space into which said sealing substance is to flow.

[0023] In any event the sealing substance is designed for the specific application. Thus, to modulate the density of the sealing substance it may also comprise barite or a light weight polymer. Other ingredients, which may be used to adjust the properties of the sealing substance as needed for the specific application, are crystalline silicas, amorphous silicas, clays, calcium carbonate, and the like.

[0024] In another embodiment the time for said sealing substance to undergo curing in step c) is controlled by the addition of a catalyst, such as an accelerator or a retarder. The catalyst such as an accelerator or a retarder may be admixed as part of the sealing substance when this substance is prepared in accordance with the determined parameters under step a). In this case, the curing time must be designed so as to allow the placing of the sealing substance at the location(s) as well as the flow of the sealing substance into the annular space. In another embodiment the sealing substance and the catalyst, such as an accelerator or a retarder, are mixed in-situ using a downhole mixer. This eliminates the need for having substantially no change of the viscoelastic properties of the sealing substance during the transfer of the sealing substance from the surface to its downhole position where injection is to take place. Such downhole mixers are known in the art, see e.g. US 5,582,251.

[0025] In another embodiment the sealing substance exhibits low curing shrinkage, such as less than 2% or less than 1%. In another embodiment the sealing substance exhibits no curing shrinkage or exhibits expansion upon curing. One way to reduce curing shrinkage or to invoke expansion upon curing is to use a sealing substance comprising a material which expands upon absorption of water, e.g. wood fibres and the like.

[0026] In another embodiment, the sealing substance comprise a filler material determining the mechanical properties of the substance after curing.

[0027] In another embodiment wherein in said step c) said sealing substance is placed at said one or more location(s) using a system for injection of a substance into an annular space. A system for injection is based on the use of pressure in order to inject the fluid. In another embodiment the placing of the sealing substance at one or more locations are performed by an assembly inserted into said well tubular, said assembly comprising: a cutting part capable of making a hole through said well tubular, a substance chamber for storage of said sealing substance, and an injection part capable of injecting said sealing substance into said annular space. Examples of such assemblies for injection of sealing substances may be found in US 20070209797. In another embodiment, in said step c) said sealing substance is placed at said one or more location(s) via a single hole in said well tubular or in said pipes.

[0028] In another aspect, the present invention provides a method for removal of one or more seals in an annular space between a well tubular and the surrounding formation or between pipes of a wellbore system, which seals have been provided by the method according to the present invention, said method for removal comprising heating said seals to a temperature of at least 250 °C, such as 300 °C.

[0029] The description herein of any aspect or embodiment of the invention using terms such as "comprising", "having," "including," or "containing" with reference to an element or elements is intended to provide support for a similar aspect or embodiment of the invention that "consists of", "consists essentially of", or "substantially comprises" that particular element or elements, unless otherwise stated or clearly contradicted by context (e.g., a composition described herein as comprising a particular element should be understood as also describing a composition consisting of that element, unless otherwise stated or clearly contradicted by context).

[0030] All headings and sub-headings are used herein for convenience only and should not be construed as limiting the invention in any way.

EXAMPLE

Example 1

[0031] Lab experiments have shown that normal epoxy will slump, float, and/or disperse in water and oil. The fluid system as described in this document will however behave as shown in figure 2, as confirmed by a series of lab experiments performed.

[0032] Current Laboratory work will firm up the initial data regarding the fluid composition in such a manner that a performance envelope for the fluid systems is established. This performance envelope will contain but is not limited to:
Pressure and temperature as a function of hardening time per fluid system, which contains a mixture of fluids and at least one solid. This solid can consist of a hollow structure (gas filled) therewith reducing the overall density of the fluid.

Claims

1. Method for providing one or more seals in an annular space between a well tubular and the surrounding formation or between pipes of a wellbore system, said method comprising the steps of

a) determining the in-situ temperature, pressure, earth formation properties and fluid(s) present at the position(s) where said one or more seals are desired,

b) providing a sealing substance which is a setting epoxy based, phenolic based or polyester based fluid comprising at least one solid component and said sealing substance having physical and fluid dynamic properties compatible with the in-situ parameters determined in step a), wherein the density of said sealing substance is in the range from 700 kg/m³ to 1400 kg/m³, and said sealing substance has a density, which is either lower or higher than the density of the fluid(s) determined in step a).

c) placing said sealing substance at one or more locations allowing it to flow into the annular space and undergo curing to form said one or more seals

wherein said sealing substance has thixotropic properties, which are compatible with the parameters determined in step a).

2. The method according to claim 1, wherein in said step c) said sealing substance is placed at said one or more location(s) using a system for injection of a substance into an annular space.

3. The method according to any of the preceding claims, wherein the placing of said sealing substance at one or more locations is performed by an assembly inserted into said well tubular, said assembly comprising: a cutting part capable of making a hole through said well tubular, a substance chamber for storage of said sealing substance, and an injection part capable of injecting said sealing substance into said annular space.

4. The method according to any of the preceding claims, wherein said sealing substance comprises silica flakes.

5. The method according to any of the preceding claims, wherein said sealing substance comprises carbon fibres.

6. The method according to any of the preceding claims, wherein said sealing substance comprises barite.

7. The method according to any of the preceding claims, wherein the time for said sealing substance to undergo curing in step c) is controlled by the addition of a catalyst, such as an accelerator or a retarder.

8. The method according to any of the preceding claims, wherein said sealing substance exhibits low curing shrinkage, such as less than 2% or less than 1%.

9. The method according to any of the preceding claims, wherein said sealing substance exhibits no curing shrinkage or exhibits expansion upon curing.

10. The method according to claim 9, wherein said sealing substance comprises wood fibres.

11. The method according to any of the preceding claims, wherein in said step c) said sealing substance is placed at said one or more location(s) via a single hole in said well tubular or in said pipes.

12. Method for removal of one or more seals in an annular space between a well tubular and the surrounding formation or between pipes of a wellbore system, which seals have been provided by the method according to any of claims 1-11, said method for removal comprising heating said seals to a temperature of at least 250°C, such as 300 °C.

Ansprüche

1. Verfahren zur Bereitstellung einer oder mehrerer Dichtungen in einem ringförmigen Raum zwischen einem Brunnenrohr und der umgebenden Formation oder zwischen Rohren eines Bohrlochsystems, welches Verfahren die folgenden Schritte umfasst

a) Bestimmen der Temperatur, des Drucks, der Erdformationseigenschaften und des Fluids bzw. der Fluide vor Ort in der bzw. den Position(en), wo die eine oder mehrere Dichtungen erwünscht ist bzw. sind,

b) Bereitstellen eines Abdichtungsstoffes, der ein verhärtendes epoxidbasiertes, phenolbasiertes oder polyesterbasiertes Fluid ist, umfassend mindestens eine feste Komponente, und indem der Abdichtungsstoff physikalische und fluiddynamische Eigenschaften aufweist, die mit den in Schritt a) bestimmten Vor-Ort-Parametern kompatibel sind, wobei die Dichte des Abdichtungsstoffes im Bereich von 700 kg/m³ bis 1400 kg/m³ ist, und der Abdichtungsstoff eine Dichte aufweist, die entweder niedriger oder höher als die Dichte des Fluids bzw. der Fluide ist, bestimmt in Schritt a).

c) Anbringen des Abdichtungsstoffes an eine oder mehrere Stellen, damit er in den ringförmigen Raum fließen kann und aushärtet zur Bildung der einen oder mehreren Dichtungen,

wobei der Abdichtungsstoff thixotropische Eigenschaften aufweist, die mit den in Schritt a) bestimmten Parametern kompatibel sind.

2. Verfahren nach Anspruch 1, wobei der Abdichtungsstoff in Schritt c) an die eine oder mehrere Stellen unter Verwendung eines Systems zum Einspritzen eines Stoffes in einen ringförmigen Raum angebracht wird.

3. Verfahren nach einem der vorgehenden Ansprüche, wobei die Anbringung des Abdichtungsstoffes an eine oder mehrere Stellen durch eine in das Brunnenrohr eingeführte Anordnung ausgeführt wird, welche Anordnung Folgendes umfasst: einen Schneidteil, der ein Loch durch das Brunnenrohr erzeugen kann, eine Stoffkammer zur Lagerung des Abdichtungsstoffes und einen Einspritzteil, der den Abdichtungsstoff in den ringförmigen Raum einspritzen kann.

4. Verfahren nach einem der vorgehenden Ansprüche, wobei der Abdichtungsstoff Siliziumflocken umfasst.

5. Verfahren nach einem der vorgehenden Ansprüche, wobei der Abdichtungsstoff Kohlefasern umfasst.

6. Verfahren nach einem der vorgehenden Ansprüche, wobei der Abdichtungsstoff Baryt umfasst.

7. Verfahren nach einem der vorgehenden Ansprüche, wobei der Zeitraum, in dem der Abdichtungsstoff in Schritt c) Aushärtung unterworfen wird, durch Zusatz eines Katalysators wie beispielsweise eines Beschleunigers oder eines Verzögerers gesteuert wird.

8. Verfahren nach einem der vorgehenden Ansprüche, wobei der Abdichtungsstoff einen geringen Härtungsschrumpf wie beispielsweise weniger als 2% oder weniger als 1% vorweist.

9. Verfahren nach einem der vorgehenden Ansprüche, wobei der Abdichtungsstoff keinen Härtungsschrumpf oder Ausweitung beim Aushärten vorweist.

10. Verfahren nach Anspruch 9, wobei der Abdichtungsstoff Holzfasern umfasst.

11. Verfahren nach einem der vorgehenden Ansprüche, wobei der Abdichtungsstoff in Schritt c) an die eine oder mehrere Stellen über ein einziges Loch im Brunnenrohr oder in den Rohren angebracht wird.

12. Verfahren zum Entfernen einer oder mehrerer Dichtungen in einem ringförmigen Raum zwischen einem Brunnenrohr und der umgebenden Formation oder zwischen Rohren eines Bohrlochsystems, welche Dichtungen durch das Verfahren nach einem der Ansprüche 1-11 bereitgestellt sind, wobei das Verfahren zum Entfernen das Aufwärmen der Dichtungen auf eine Temperatur von mindestens 250° C, wie beispielsweise 300° C, umfasst.

Revendications

1. Procédé de fourniture d'un ou de plusieurs joints d'étanchéité dans un espace annulaire entre un puits tubulaire et la formation environnante ou entre des conduites d'un système de forage de puits, ledit procédé comprenant les étapes consistant à

a) déterminer la température in situ, la pression, les propriétés de formation de la terre et le ou les fluides présents à la ou aux positions où un ou plusieurs joints d'étanchéité sont souhaités,

b) fournir une substance d'étanchéité qui est un fluide à base d'époxy à durcissement, à base phénolique ou à base de polyester comprenant au moins un composant solide et ladite substance d'étanchéité ayant des propriétés physiques et dynamiques de fluides compatibles avec les paramètres in situ déterminés à l'étape a), dans lequel la densité de ladite substance d'étanchéité est comprise dans l'intervalle allant de 700 kg/m³ à 1400 kg/m³, et ladite substance d'étanchéité présente une densité qui est inférieure ou supérieure à la densité du ou des fluides déterminés à l'étape a),

c) placer ladite substance d'étanchéité à un ou plusieurs emplacements lui permettant de s'écouler dans l'espace annulaire et de subir un durcissement pour former ledit ou lesdits joints d'étanchéité,

dans lequel ladite substance d'étanchéité présente des propriétés thixotropes compatibles avec les paramètres déterminés à l'étape a).

2. Procédé selon la revendication 1, dans lequel, dans ladite étape c), ladite substance d'étanchéité est placée sur ledit ou lesdits emplacements en utilisant un système pour l'injection d'une substance dans un espace annulaire.

3. Procédé selon l'une quelconque des revendications précédentes, dans lequel la mise en place de ladite substance d'étanchéité en un ou plusieurs emplacements est réalisée par un ensemble inséré dans ledit puits tubulaire, ledit ensemble comprenant : une partie coupante capable de faire un trou à travers ledit puits tubulaire, une chambre de substance pour stocker ladite substance d'étanchéité et une partie d'injection capable d'injecter ladite substance d'étanchéité dans ledit espace annulaire.

4. Procédé selon l'une quelconque des revendications précédentes, dans lequel ladite substance d'étanchéité comprend des flocons de silice.

5. Procédé selon l'une quelconque des revendications précédentes, dans lequel ladite substance d'étanchéité comprend des fibres de carbone.

6. Procédé selon l'une quelconque des revendications précédentes, dans lequel ladite substance d'étanchéité comprend de la baryte.

7. Procédé selon l'une quelconque des revendications précédentes, dans lequel le temps nécessaire pour que ladite substance d'étanchéité subisse un durcissement à l'étape c) est commandé par l'addition d'un catalyseur, tel qu'un accélérateur ou un retardateur.

8. Procédé selon l'une quelconque des revendications précédentes, dans lequel ladite substance d'étanchéité présente un faible retrait de durcissement, tel que moins de 2% ou moins de 1%.

9. Procédé selon l'une quelconque des revendications précédentes, dans lequel ladite substance d'étanchéité ne présente ni de retrait de durcissement ni d'expansion lors du durcissement.

10. Procédé selon la revendication 9, dans lequel ladite substance d'étanchéité comprend des fibres de bois.

11. Procédé selon l'une quelconque des revendications précédentes, dans lequel, dans ladite étape c), ladite substance d'étanchéité est placée au niveau dudit ou desdits emplacements par l'intermédiaire d'un trou unique dans ledit puits tubulaire ou dans lesdits tuyaux.

12. Procédé pour enlever un ou plusieurs joints d'étanchéité dans un espace annulaire entre un puits tubulaire et la formation environnante ou entre des conduits d'un système de puits de forage, ces joints d'étanchéité étant fournis par le procédé selon l'une quelconque des revendications 1 à 11, ledit procédé pour enlever comprenant le chauffage desdits joints d'étanchéité à une température d'au moins 250°C, par exemple d'environ 300°C.

Drawing